J/MNRAS/470/755      Galaxy mergers and AGN activity            (Hewlett+, 2017)
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The redshift evolution of major merger triggering of luminous AGNs:
a slight enhancement at z ~ 2.
    Hewlett T., Villforth C., Wild V., Mendez-Abreu J., Pawlik M., Rowlands K.
   <Mon. Not. R. Astron. Soc., 470, 755-770 (2017)>
   =2017MNRAS.470..755H    (SIMBAD/NED BibCode)
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ADC_Keywords: Active gal. nuclei ; X-ray sources ; Photometry ; Morphology
Keywords: galaxies: active - galaxies: interactions - X-rays: galaxies

Abstract:
    Active galactic nuclei (AGNs), particularly the most luminous AGNs,
    are commonly assumed to be triggered through major mergers; however,
    observational evidence for this scenario is mixed. To investigate any
    influence of galaxy mergers on AGN triggering and luminosities through
    cosmic time, we present a sample of 106 luminous X-ray-selected type 1
    AGNs from the COSMOS survey. These AGNs occupy a large redshift range
    (0.5<z<2.2) and two orders of magnitude in X-ray luminosity
    (~10^43^-10^45^erg/s). AGN hosts are carefully mass and redshift
    matched to 486 control galaxies. A novel technique for identifying and
    quantifying merger features in galaxies is developed, subtracting
    GALFIT galaxy models and quantifying the residuals. Comparison to
    visual classification confirms this measure reliably picks out
    disturbance features in galaxies. No enhancement of merger features
    with increasing AGN luminosity is found with this metric, or by visual
    inspection. We analyse the redshift evolution of AGNs associated with
    galaxy mergers and find no merger enhancement in lower redshift bins.
    Contrarily, in the highest redshift bin (z~2) AGNs are ~4 times more
    likely to be in galaxies exhibiting evidence of morphological
    disturbance compared to control galaxies, at 99 per cent confidence
    level (~2.4{sigma}) from visual inspection. Since only ~15 per cent of
    these AGNs are found to be in morphologically disturbed galaxies, it
    is implied that major mergers at high redshift make a noticeable but
    subdominant contribution to AGN fuelling. At low redshifts, other
    processes dominate and mergers become a less significant triggering
    mechanism.

Description:
    High-resolution HST images of 106 X-ray-selected AGNs and 486 host
    galaxy mass and redshift-matched control galaxies from the COSMOS
    survey are analysed. Artificial AGNs (stars), matched in apparent
    magnitude to the relevant AGNs, are placed into control galaxies to
    make images equivalent. A new method for detecting disturbance in
    galaxies is developed

File Summary:
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 FileName      Lrecl  Records   Explanations
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ReadMe            80        .   This file
agnsamp.dat       97      106   AGN sample
control.dat       97      486   Control sample
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See also:
        II/284 : COSMOS Multi-Wavelength Photometry Catalog (Capak+, 2007)
 J/ApJS/172/29 : XMM-Newton survey in COSMOS field. I. (Hasinger+, 2007)
 J/A+A/497/635 : XMM-Newton wide-field survey in COSMOS field (Cappelluti+ 2009)

Byte-by-byte Description of file: agnsamp.dat control.dat
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   Bytes Format Units   Label     Explanations
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   1-  7  I7    ---     XID       Identification number,
                                   XMMC NNNN in Simbad for AGN,
                                   COSMOS NNNNNNN in Simbad for galaxies
   9- 16  F8.4  deg     RAdeg     Right ascension (J2000)
  18- 24  F7.5  deg     DEdeg     Declination (J2000)
  26- 32  F7.4  mag     mPS       Point source magnitude
  34- 39  F6.4  mag   e_mPS       rms uncertainty on mPS
  41- 48  F8.4  mag     mGal      ?=-99 Galaxy magnitude
  50- 57  F8.4  mag   e_mGal      ?=-99 rms uncertainty on mGal
  59- 68  F10.6 kpc     Re        ?=-99 Effective radius
  70- 79  F10.6 kpc   e_Re        ?=-99 rms uncertainty on Re
  81- 88  F8.4  ---     n         ?=-99 Sersic number
  90- 97  F8.4  ---   e_n         ?=-99 rms uncertainty on n
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History:
    From electronic version of the journal

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(End)                                      Patricia Vannier [CDS]    23-Apr-2020